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A new imine-induced 1,2-boronate migration has been developed for achieving chemo- and stereoselective dearomative coupling of C3-substituted indoles and bi-electrophilic β-imino boronic esters, providing rapid access to complex chiral indoline boronic esters with four stereocenters including an all-carbon quaternary stereocenter and a tertiary α-aminoboronic ester. In contrast, coupling of indoles without C3 substitution and β-imino boronic esters provided tetrahydro-1H-pyrido[4,3-b]indoles via imine-induced 1,2-boronate migration followed by deborylative rearomatization.

Herein we report a highly efficient and enantiospecific borylation method to synthesize a wide range of enantiopure (>99 % ee) α-amino tertiary boronic esters. The configurationally stable α-N-Boc substituted tertiary organolithium species and pinacolborane (HBpin) underwent enantiospecific borylation at -78 °C with the formation of a new stereogenic C-B bond. This reaction has a broad scope, enabling the synthesis of various α-amino tertiary boronic esters in excellent yields and, importantly, with universally excellent enantiospecificity (>99 % es) and complete retention of configuration.

Carbometalation of alkenes with stereocontrol offers an important opportunity for asymmetric C-C bond formation. However, the scope of catalytic stereoselective carbometalation of alkenes had until recently been limited to electronically biased alkenes or those with the presence of directing groups or other auxiliary functionalities to overcome the challenge associated with regio- and stereoselectivity. Catalytic asymmetric carbometalation of unactivated alkenes on the other hand remained as a formidable challenge. To address this long-standing problem, we sought to develop Zr-catalyzed asymmetric carboalumination of alkenes (namely, ZACA reaction) encouraged by our discovery of Zr-catalyzed alkyne carboalumination in 1978. Zr-catalyzed methylalumination of alkynes (ZMA) shows high regioselectivity and nearly perfect stereoselectivity. Its mechanistic studies have revealed that the ZMA reaction involves acyclic carbometalation with "superacidic" bimetallic reagents generated by interaction between two Lewis acids, i.e., alkylalanes and 16-electron zirconocene derivatives through dynamic polarization and ate complexation, affectionately termed as the "two-is-better-than-one" principle. With the encouraging results of Zr-catalyzed carboalumination of alkynes in hand, we sought to develop its alkene version for discovering a catalytic asymmetric C-C bond-forming reaction by using alkylalanes and suitable chiral zirconocene derivatives, which would generate "superacidic" bimetallic species to promote the desired carbometalation of alkenes. However, this proved to be quite challenging. Three major competing side reactions occur, i.e., (i) β-H transfer hydrometalation, (ii) bimetallic cyclic carbometalation, and (iii) Ziegler-Natta polymerization. The ZACA reaction was finally discovered by employing Erker's (-)-(NMI)

Herein, we report a zirconium-catalyzed enantio- and diastereoselective inter/intramolecular double carboalumination of unactivated 2-substituted 1,5-dienes, which provides efficient and direct access to chiral cyclopentanes through the generation of two stereocenters, including one all-carbon quaternary stereocenter, generally with excellent diastereo- and high enantioselectivity. This tandem carboalumination process creates two new C−C bonds as well as one C−Al bond, which can be oxidized in situ with O2 or hydrolyzed. Furthermore, the obtained chiral cyclopentanes can be readily functionalized to provide various chiral compounds.

Despite recent advances of asymmetric synthesis, the preparation of enantiomerically pure (≥99% ee) compounds remains a challenge in modern organic chemistry. We report here a strategy for a highly enantioselective (≥99% ee) and catalytic synthesis of various γ- and more-remotely chiral alcohols from terminal alkenes via Zr-catalyzed asymmetric carboalumination of alkenes (ZACA reaction)-Cu- or Pd-catalyzed cross-coupling. ZACA-in situ oxidation of tert-butyldimethylsilyl (TBS)-protected ω-alkene-1-ols produced both (R)- and (S)-α,ω-dioxyfunctional intermediates (3) in 80-88% ee, which were readily purified to the ≥99% ee level by lipase-catalyzed acetylation through exploitation of their high selectivity factors. These α,ω-dioxyfunctional intermediates serve as versatile synthons for the construction of various chiral compounds. Their subsequent Cu-catalyzed cross-coupling with various alkyl (primary, secondary, tertiary, cyclic) Grignard reagents and Pd-catalyzed cross-coupling with aryl and alkenyl halides proceeded smoothly with essentially complete retention of stereochemical configuration to produce a wide variety of γ-, δ-, and ε-chiral 1-alkanols of ≥99% ee. The MαNP ester analysis has been applied to the determination of the enantiomeric purities of δ- and ε-chiral primary alkanols, which sheds light on the relatively undeveloped area of determination of enantiomeric purity and/or absolute configuration of remotely chiral primary alcohols.

The existence of the rare six-membered and intramolecular C-H···F-C hydrogen-bond has been experimentally proven in the gas phase and in the solid state recently. However, the effect of the substituents on this C-H···F-C hydrogen-bond system has never been reported. In view of the importance of this type of C-H···F-C H-bonding whose weak interaction has been found critical in nanotechnology and biological systems, the nine functional groups composed of electron donating and electron withdrawing groups are inserted into this C-H···F-C interaction to study the group effect on the hydrogen bonding. Group effects on this C-H···F-C H-bonding system have been found, and their effects on the H-bonding system have been found to be tunable.

A highly enantioselective and widely applicable method for the synthesis of various chiral 2-alkyl-1-alkanols, especially those of feeble chirality, has been developed. It consists of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and palladium- or copper-catalyzed cross-coupling. By virtue of the high selectivity factor (E) associated with iodine, either (S)- or (R)-enantiomer of 3-iodo-2-alkyl-1-alkanols (1), prepared by ZACA reaction of allyl alcohol, can be readily purified to the level of ≥99% ee by lipase-catalyzed acetylation. A variety of chiral tertiary alkyl-containing alcohols, including those that have been otherwise difficult to prepare, can now be synthesized in high enantiomeric purity by Pd- or Cu-catalyzed cross-coupling of (S)-1 or (R)-2 for introduction of various primary, secondary, and tertiary carbon groups with retention of all carbon skeletal features. These chiral tertiary alkyl-containing alcohols can be further converted into the corresponding acids with full retention of the stereochemistry. The synthetic utility of this method has been demonstrated in the highly enantioselective (≥99% ee) and efficient syntheses of (R)-2-methyl-1-butanol and (R)- and (S)-arundic acids.

ConspectusCarbometalation of alkenes with stereocontrol offers an important opportunity for asymmetric C–C bond formation. However, the scope of catalytic stereoselective carbometalation of alkenes had until recently been limited to electronically biased alkenes or those with the presence of directing groups or other auxiliary functionalities to overcome the challenge associated with regio- and stereoselectivity. Catalytic asymmetric carbometalation of unactivated alkenes on the other hand remained as a formidable challenge. To address this long-standing problem, we sought to develop Zr-catalyzed asymmetric carboalumination of alkenes (namely, ZACA reaction) encouraged by our discovery of Zr-catalyzed alkyne carboalumination in 1978. Zr-catalyzed methylalumination of alkynes (ZMA) shows high regioselectivity and nearly perfect stereoselectivity. Its mechanistic studies have revealed that the ZMA reaction involves acyclic carbometalation with “superacidic” bimetallic reagents generated by interaction betwe...

Pd-catalyzed cross-coupling giving aryl–aryl, alkenyl–aryl, aryl–alkenyl, alkynyl–aryl, and alkynyl–alkenyl products exhibited ultra-high turnover numbers (TONs) of 0.7×10~0.69×10 by using organozincs generated in situ by treatment of the corresponding organolithiums with dry ZnBr2. Additionally, the hydrozirconation–Pd-catalyzed cross-coupling tandem processes via treatment of 1-alkynes with Bu2AlH-ZrCp2Cl2 followed by selective (≥98%) alkenyl–alkenyl coupling with either (E)or (Z)-ethyl 3-bromoacrylate exhibited high TONs of 0.9×10~0.81×10. Furthermore, Pd-catalyzed cross-coupling of 2-thienylzinc bromide and 1iodo-4-nitrobenzene also showed a high TON of 0.87×10.

Despite major advances in the syntheses of strictly (≥98%) regio- and stereodefined alkenes via “elementometalation”[1]–Pd- or Ni-catalyzed cross-coupling developed since 1976,[2]-[4] efficient and highly (≥98%) selective syntheses of tri- and tetrasubstituted alkenes continue to provide major synthetic challenges. The Zr-catalyzed alkyne carboalumination–Negishi coupling[3][4] (Eq. 1 in Scheme 1) has provided a highly selective and widely used method for the synthesis of trisubstituted alkenes.[4b] Although this method is broad in synthetic scope with respect to R1 of the starting alkyne (R1C≡CH), the R2 group of the organoalanes to be added to R1C≡CH has been practically limited to Me, and a limited number of alkyl groups including allyl and benzyl groups.[3–6] On the other hand, in an alkyne bromoboration–Negishi-Suzuki tandem cross-coupling process (Eq. 2 in Scheme 1) reported by Suzuki in 1988,[7] bromoboration of R1C≡CH is followed by incorporation of both R2 and R3 groups by Pd-catalyzed cross-coupling reactions of wide synthetic scopes, thereby promising to provide a method of very wide applicability for synthesizing trisubstituted alkenes. In reality, however, all reported examples[7] of Eq. 2 in Scheme 1 and of its modification involving double Negishi coupling reactions[8,9] (Eq. 3 in Scheme 1) involve the use of only alkylethynes, even though haloboration of aryl- and alkenyl-substituted ethynes are known to proceed well.[10] Scheme 1 Highly (≥98%) selective “elementometalation” –Pd-catalyzed cross-coupling routes to trisubstituted alkenes. As readily suspected, competitive debromoboration of 2 to revert to the starting alkynes would be the main cause of difficulty in the Pd-catalyzed cross-coupling of 2, and the fact that those derived from aryl- and alkenyl-substituted ethynes are benzylic and allylic bromides, respectively, besides being alkenyl bromides must undoubtedly be responsible for their significantly higher propensity to undergoing debromoboration, as compared with that of alkylethyne-derived 2. Thus, for example, the reaction of 2a, generated by bromoboration of phenylethyne followed by treatment with pinacol, with (E)-1-octenylzinc bromide in the presence of Pd(DPEphos)Cl2 (0.5 mol %) at 23 °C for 2 h led to the formation of the desired 3a in

In situ OH metalation with i Bu 2 AlH and hydrozirconation with HZrCp 2 Cl of HOCH 2 C CH, ( E )-HOCH 2 CH CHC CH, and HOCH 2 C CCH 3 followed by Pd-catalyzed alkenyl–alkenyl coupling with ( E )-BrCH CHCO 2 Et and ( E )-BrCH C(Me)CO 2 Et using PEPPSI-IPr ( 7 ) as a catalyst provides a highly efficient and selective (⩾98% all- E ) route to ω-hydroxy di- and trienoic acid esters ( 1a – 6a ). The corresponding phosphonate esters ( 1c – 4c ) of ⩾98% isomeric purity can be obtained via conventional bromination–phosphonation in >80% yields. As expected, their carbonyl olefination is ca. 85–90% E -selective with alkyl aldehydes but ⩾98% E -selective with PhCHO and some α,β-unsaturated aldehydes under the conditions used.

Zr-catalyzed methylalumination of 3-butyn-1-ols followed by AlCl3-promoted stereoisomerization at 50 °C for 6 h provides 4-iodo-3-methyl-3-buten-1-ols 2b and 6 of ≥98 Z configuration in 87 and 67% yields, respectively. (Z)-1,4-Diiodo-2-methyl-1-butene (1b) obtainable by iodination of 2b is a valuable synthon for efficient and selective syntheses of (Z)-alkene containing isoprenoids.

Substituent effects on the open shell N-H···O═C hydrogen-bond has never been reported. This study examines how 12 functional groups composed of electron donating groups (EDG), halogen atoms and electron withdrawing groups (EWG) affect the N-H···O═C hydrogen-bond properties in a six-membered cyclic model system of O═C(Y)-CH═C(X)N-H. It is found that group effects on this open shell H-bonding system are significant and have predictive trends when X = H and Y is varied. When Y is an EDG, the N-H···O═C hydrogen-bond is strengthened; and when Y is an EWG, the bond is weakened; whereas the variation in electronic properties of X group do not exhibit a significant impact upon the hydrogen bond strength. The structural impact of the stronger N-H···O═C hydrogen-bond are (1) shorter H and O distance, r(H···O) and (2) a longer N-H bond length, r(NH). The stronger N-H···O═C hydrogen-bond also acts to pull the H and O in toward one another which has an effect on the bond angles. Our findings show that there is a linear relationship between hydrogen-bond angle and N-H···O═C hydrogen-bond energy in this unusual H-bonding system. In addition, there is a linear correlation of the r(H···O) and the hydrogen bond energy. A short r(H···O) distance corresponds to a large hydrogen bond energy when Y is varied. The observed trends and findings have been validated using three different methods (UB3LYP, M06-2X, and UMP2) with two different basis sets.

Hydroboration of 1-bromo-1-alkynes with dibromoborane followed by addition of 3 or 4 equiv of Me2Zn provides an efficient and selective route to (Z)-2-alkenyldimethylboranes (3) or (Z)-2-alkenylmethylzincs (4), respectively, which have been successfully applied to one-pot Suzuki (B-I) or Negishi (Zn-I) coupling in some less demanding cases. However, in more demanding cross-coupling reactions, only the use of either (Z)-2-alkenyliodides (5) or the alkenylzincs prepared from lithiation and then zincation of 5 proves to be highly satisfactory (Zn-II or Zn-III protocol). On the contrary, the corresponding organoboron coupling under B-II or B-III protocol appears to be less satisfactory. Preliminary studies indicate that certain substituents proximal to trisubstituted alkenes seriously affect the course of the desired alkenylboron cross-coupling.

Two highly efficient protocols for enantioselective synthesis of 2,4-dimethyl-1-penten-1,5-ylidene derivatives involve the combined use of the Zr-catalyzed methylalumination of alkynes (ZMA) and the Zr-catalyzed asymmetric carboalumination of alkenes (ZACA). The ZMA/ZACA protocol has been applied to the synthesis of a nafuredin intermediate 14 and a potential intermediate 18 for milbemycin beta 3, while the ZACA/ZMA protocol has been applied to the synthesis of a (-)-bafilomycin A(1) intermediate 25.

ZACA-lipase-catalyzed acetylation tandem reactions provide highly efficient and selective routes to either (R)- or (S)-2-methyl-1-alkanols, making, for the first time, the ZACA-based asymmetric synthesis of 2-methyl-1-alkanols widely applicable and satisfactory.

The Pd- or Ni-catalyzed cross-coupling reactions of organometals containing Zn, Al, Zr, and B as well as related reactions of Mg and several other metals collectively represent the most widely appl...

Shortly after the discovery of Zr-catalyzed carboalumination of alkynes in 1978, we sought expansion of the scope of this reaction so as to develop its alkene version for catalytic asymmetric C–C bond formation, namely the ZACA (Zr-catalyzed asymmetric carboalumination of alkenes). However, this seemingly easy task proved to be quite challenging. The ZACA reaction was finally discovered in 1995 by suppressing three competitive side reactions, i.e., (i) cyclic carbometalation, (ii) β-H transfer hydrometalation, and (iii) alkene polymerization. The ZACA reaction has been used to significantly modernize and improve syntheses of various natural products including deoxypolypropionates and isoprenoids. This review focuses on our recent progress on the development of ZACA–lipase-catalyzed acetylation–transition metal-catalyzed cross-coupling processes for highly efficient and enantioselective syntheses of a wide range of chiral organic compounds with ultra-high enantiomeric purities.

A new strategy for highly concise, convergent, and enantioselective access to polydeoxypropionates has been developed. ZACA-Pd-catalyzed vinylation was used to prepare smaller deoxypropionate fragments, and then two key sequential Cu-catalyzed stereocontrolled sp(3)-sp(3) cross-coupling reactions allowed convergent assembly of smaller building blocks to build-up long polydeoxypropionate chains with excellent stereoselectivity. We employed this strategy for the synthesis of phthioceranic acid, a key constituent of the cell-wall lipid of Mycobacterium tuberculosis, in just 8 longest linear steps with full stereocontrol.

Iteration of a Pd-catalyzed reaction of alkynyl- and oligoynylzincs with (E)-ICH=CHCl followed by metalation-termination with electrophiles(E) has provided a linear route to conjugated tri- and tetraynes, and Pd-catalyzed monoalkynylation of 1,1-dibromoenynes accompanied by dehydrobromination has provided a convergent route to conjugated tri- , tetra- , and pentaynes. Both display unprecedented high efficiency and selectivity. [reaction: see text]

Variously substituted 1,4-dienes containing a terminal vinyl (H2C CH) group, readily undergo the ZACA reaction with Me3Al and higher alkylalanes in a 1:1 molar ratio in the presence of a catalytic amount (1–5 mol %) of bis[(1-neomenthyl)indenyl]zirconium dichloride in good yields and in good enantioselectivity (70–92% ee), thereby providing an efficient and convenient route to various alkene-containing chiral natural products. Only the reaction of the parent 1,4-pentadiene is accompanied by extensive racemization.

The reaction of alkynylzinc bromides with benzyl bromides or chlorides in the presence of a catalytic amount of Pd(DPEphos)Cl2 in THF at 23 °C cleanly produces the corresponding benzylated alkynes in 73–97% yields. With 10−3 mol % of Pd(DPEphos)Cl2, the maximum turnover number of 7.1 × 104 has been observed for the formation of PhC CCH2Ph.

Palladium-catalyzed reactions of unsaturated organozincs with aryl or alkenyl iodides can exhibit turnover numbers (TONs) over 105 (>70% product yields). Under the conditions employed, Zn, B, and In appear to be the three most favorable metals, followed by Al(Zn) and Zr(Zn), whereas TONs observable with Sn, Cu, and Mn have been significantly lower.

One-pot conversion of alkynes to regio- and stereodefined alkenylmetals containing Al and Zr via hydrometalation or carbometalation followed by their Pd-catalyzed cross-coupling with (E)-ICH=CHBr or (E)-ICH=CHCl proceeds cleanly and selectively to give the corresponding 1-halo-1,3-dienes in excellent yields using a catalyst system consisting of Cl(2)Pd(DPEphos), DIBAL-H, and TFP (catalyst A) with InCl(3) as a cocatalyst.

Tetra-substituted zirconacyclopentadiene derivatives, obtainable via in situ generation of zirconacyclopropenes and their cyclic carbozirconation with alkynes, can be treated with alkynyllithiums to induce 1,2-migration accompanied by aromatization and protonolysis, leading to the formation of penta-substituted benzene derivatives, in which all five substituted may be different.

trans-Selective (≥98%) monoalkynylation of 1,1-dibromo-1-alkenes and 1,1-dichloro-1-alkenes catalyzed by Cl2Pd(DPEphos) followed by stereospecific methylation with Me2Zn or MeZnX (X= Cl or Br) catalyzed by Pd(tBu3P)2 provides an efficient and stereoselective (≥98%) route to 5, convertible to a wide variety of enynes and conjugated dienes. In the cases of 1,1-dibromo-1-alkenes, the Sonogashira alkynylation may also be satisfactory, but it is distinctly less satisfactory than the alkynylzinc reaction in cases where 1,1-dichloro-1-alkenes are used.

Various unsymmetrically substituted conjugated diynes can be synthesized in a completely “pair”-selective manner via Pd-catalyzed reaction of terminal alkynes with 1,1-dichloroethylene in the presence of Pd(PPh3)4 followed by elimination with 2 equiv of lithium diisopropylamide (LDA), zincation with ZnBr2 or ZnCl2, and Pd-catalyzed cross-coupling with aryl and alkenyl iodides and bromides. The desired unsymmetrically substituted conjugated diynes have been obtained in >80% yields except in two cases where an alkenylzinc reagent generated in situ from (E)-3-iodo-2-propenol was used. The use of 1,1-dichloroethylene renders this method more economical than those involving 1,2-dihaloethylenes previously reported.

Treatment of (Z)-5-alkyl-2-en-4-ynoic acids ( 1 ), prepared by the Pd-catalyzed alkynylzinc–β-haloacrylic acid coupling, with 5–10 mol% of ZnBr2 can produce 6-alkyl-2H-pyran-2-ones ( 2 ) along with minor amounts of (Z)-5-alkylidenefuran-2(5H)-ones ( 3 ) in >90% combined yields, with often very high (≈95/5) pyranone/furanone ratios. On the other hand, lactonization of 1 catalyzed by Ag2CO3 provides a selective synthesis of (Z)-5-alkylidenefuran-2(5H)-ones ( 3 ) in >90% yields along with minor amounts (≤5%) of 2 .

This paper describes (a) a very brief history leading to the birth of the Pd-catalyzed cross-coupling, (b) its birth in the mid-1970s, (c) the development of the Pd-catalyzed cross-coupling with organometals containing Zn, Al, Zr, and Mg (the ‘first-generation’ Pd-catalyzed cross-coupling) in the 1970s, (d) seeding of the Pd-catalyzed cross-coupling with organometals containing Sn, B, and Si (the ‘second-generation’ Pd-catalyzed cross-coupling) in the late-1970s, and (e) further developments in the author's group in the 1980s.

[reaction: see text] A linear iterative method for the construction of (all-E)-oligoenes of the (CH=CH)n type via hydrozirconation-palladium-catalyzed cross-coupling with (E)-1-bromo-4-trimethylsilyl-1-buten-3-yne is described. This method promises to provide an efficient, selective, and general route to oligoene macrolide antibiotics and other related natural products.

The discovery, methodological developments, including those for separation­purification of chiral flexible primary alcohols, and their applications to the syntheses of some natural products of the titled reaction are discussed.

Chiral compounds arising from the replacement of hydrogen atoms by deuterium are very important in organic chemistry and biochemistry. Some of these chiral compounds have a non-measurable specific rotation, owing to very small differences between the isotopomeric groups, and exhibit cryptochirality. This particular class of compounds is difficult to synthesize and characterize. Herein, we present a catalytic and highly enantioselective conversion of terminal alkenes to various β and more remote chiral isotopomers of 1-alkanols, with ≥99 % enantiomeric excess (ee), by the Zr-catalyzed asymmetric carboalumination of alkenes (ZACA) and Cu-catalyzed cross-coupling reactions. ZACA-in situ iodinolysis of allyl alcohol and ZACA-in situ oxidation of TBS-protected ω-alkene-1-ols protocols were applied to the synthesis of both (R)- and (S)-difunctional intermediates with 80-90 % ee. These intermediates were readily purified to provide enantiomerically pure (≥99 % ee) compounds by lipase-catalyzed acetylation. These functionally rich intermediates serve as very useful synthons for the construction of various chiral isotopomers of 1-alkanols in excellent enantiomeric purity (≥99 % ee) by introducing deuterium-labeled groups by Cu-catalyzed cross-coupling reactions without epimerization.

Organic molecules and polymers with extended π-conjugation are appealing as advanced electronic materials, and have already found practical applications in thin-film transistors, light emitting diodes, and chemical sensors. Transition metal (TM)-catalyzed cross-coupling methodologies have evolved over the past four decades into one of the most powerful and versatile methods for C–C bond formation, enabling the construction of a diverse and sophisticated range of π-conjugated oligomers and polymers. In this review, we focus our discussion on recent synthetic developments of several important classes of π-conjugated systems using TM-catalyzed cross-coupling reactions, with a perspective on their utility for organic electronic materials.

[structure: see text]. A highly efficient and stereoselective protocol for the syntheses of symmetrical and unsymmetrical carotenoids involving Zr-catalyzed carboalumination of conjugated oligoenynes and Pd- and Zn-catalyzed alkenyl-alkenyl coupling has been developed and applied to the syntheses of beta- and gamma-carotene and vitamin A. gamma-Carotene ofor =99% isomeric purity was prepared in three linear steps (five steps overall) from beta-ionone, enyne 8, (E)-ICH=CHBr, and (E)-Me3SiC triple bond CCH=CHBr in 32% overall yield.

The reaction of terminal alkenes with trialkylalanes in the presence of chiral (NMI) 2ZrCl2 has been shown to be 70-75% ee for methylalumination and 90-95% ee for ethyl- and higher alkylalumination. It must involve an acyclic bimetallic process. Its scope, limitations, and applications to some natural products syntheses are discussed.

The conditions for the Pd-catalyzed cross coupling of cyclic α-iodoenones, such as 2-iodo-2-cyclohexenone, with alkynylzincs have been optimized. The use of tris(o-furyl)phosphine (TFP) as a ligand and DMF as a solvent has led to the formation of α-alkynylenones in excellent yields. This optimized procedure has been applied to the synthesis of (±)-harveynone and (±)-tricholomenyn A in high yields. Investigation of related α-alkylation reactions using alkylzincs has revealed the following. Methylzinc and primary alkylzinc derivatives readily undergo Pd-catalyzed cross coupling with α-iodoenones. Although (s-Bu)2Zn also undergoes Pd-catalyzed cross coupling, only the n-Bu-substituted products were obtained. α-Benzylation and α-homobenzylation can proceed satisfactorily, whereas allylzinc and propargylzinc derivatives undergo only addition to the carbonyl group. Although some promising results have been obtained in α-homoallylation and α-homopropargylation, these reactions need to be further improved.

The reaction of aryl and alkenyl iodides and bromides with highly acidic ketones in the presence of CO (40–45 atm), NEt3 (1–2 equiv.), and 5 mol% of Cl2Pd(PPh3)2 in DMF at 100°C provides the corresponding enol carboxylates formed via trapping of putative acylpalladiums with O-enolates. In cases where alkenyl halides are used, the initially formed products can cyclize to give the corresponding lactones.

[formula: see text] Pd-catalyzed reaction of iododienes and iodoarylalkenes represented by 1, 8, and 10 under 1 atm of CO and a small amount of O2 in the presence of a base, e.g., NEt3, as well as MeOH and H2O in DMF can undergo a highly diastereoselective cyclic carbopalladation-carbonylative esterification tandem process (Type II C-Pd process) to give in high yields the corresponding ester-containing cyclization products, e.g., 2, 9, and 11, in as high as 98% diastereoselectivity.